TW201900911A - Sputter target for transparent conductive film - Google Patents

Abstract

The spattering target for transparent conductive film of the present invention comprising an oxide sintered body, the constituent elements of the oxide sintered body are In, Sn, Si and O, the content ratio of In is 25.0 mass% or more and 82.0 mass% or less in terms of In2O3, the content ratio of Sn is 15.0 mass% or more and 65.0 mass% or less in terms of SnO2, the content ratio of Si is 3.0 mass% or more and 10.0 mass% or less in terms of SiO2. The spattering target for forming conductive film of the present invention has low resistivity and can perform DC spattering, and by spattering, a transparent conductive film having high film resistivity and high chemical resistance can be formed.

Description

   Sputter target for transparent conductive film   

The present invention relates to a sputtering target for a transparent conductive film, and more specifically, to a sputtering target for a transparent conductive film that can be DC sputtered and can form a transparent conductive film with high chemical resistance.

In the transparent conductive film used in the embedded capacitive touch panel, in order to prevent the display operation from being hindered by low-frequency noise, high resistance and high transmittance are required. Because the conductive film has low resistance, the high-frequency signals used for touch sensing will be completely blocked.

This conductive film is usually formed by sputtering a sputtering target.

High-transmittance materials mainly use ITO, but because of its low resistance, ITO cannot use the conductive film of the built-in capacitive touch panel.

The technology for obtaining a high-resistance material is a technology of adding an insulating oxide to ITO, but this is a method of adding a large amount of impurities to ITO, so the optical characteristics of the conductive film will be lowered, and the crystalline disintegration of the film will cause It will reduce the chemical resistance of the conductive film. When the chemical resistance of the conductive film is low, it may be difficult to use the conductive film in applications where the conductive film is not dissolved by a chemical or the like, or inadequate applications where the conductive film is used as a thin film and has a high etching rate.

For example, Patent Document 1 discloses a of ITO as a main raw material, containing from 7.2 to 11.2 atom% of silicon, and a specific resistance of 10 ^° to 10 ³ Ω cm of a transparent conductive film. Patent Document 2 discloses a transparent conductive film having a resistivity of 0.8 to 10 × 10 ^-3 Ω cm obtained by sputtering a transparent conductive film composed of indium oxide, tin oxide, and silicon oxide with a sputtering target. However, any of the conductive films has low chemical resistance.

In addition, many high-resistance films have been proposed, but the resistance of the target used in the film formation of the film also becomes high. When the resistance of the target is high, sputtering cannot be performed with a DC power supply, and a high-resistance film must be produced with an RF power supply, which results in poor productivity.

    [Prior technical literature]         [Patent Literature]    

[Patent Document 1] Japanese Patent No. 5855948

[Patent Document 2] Japanese Patent No. 4424889

An object of the present invention is to provide a sputtering target capable of performing DC sputtering and forming a transparent conductive film having high specific resistance and high chemical resistance.

The sputtering target for a transparent conductive film of the present invention includes an oxide sintered body, the constituent elements of the oxide sintered body are In, Sn, Si, and O, and the content ratio of In is more than 25.0% by mass in terms of In ₂ O ₃ . In addition, the content ratio of Sn is 15.0% by mass or more and 65.0% by mass or less in terms of SnO ₂ , and the content ratio of Si is 3.0% by mass or more and less than 10.0% by mass in terms of SiO ₂ .

The sputtering target for a transparent conductive film preferably has a specific resistance of 2 × 10 ² Ω cm or less.

The sputtering target for a transparent conductive film preferably has a relative density of 98.0% or more.

The constituent elements of the transparent conductive film of the present invention are In, Sn, Si, and O, and the content ratio of In is 28.0% by mass or more and 87.0% by mass or less according to In ₂ O ₃ , and the content ratio of Sn is 12.0 mass by SnO ₂ conversion. % To 63.0% by mass, and the content ratio of Si is 1.0% to 9.0% by mass in terms of SiO ₂ .

The aforementioned transparent conductive film preferably has a film specific resistance of 1.0 × 10 ⁰ Ω cm or more, and preferably has an etching rate of less than 11.0 Å / sec.

The manufacturing method of the transparent conductive film of this invention is formed by sputtering the said sputtering target for transparent conductive films.

In the manufacturing method of the transparent conductive film, the specific resistance of the transparent conductive film is preferably 1.0 × 10 ⁰ Ω cm or more, and the etching rate is preferably less than 11.0 Å / sec.

The sputtering target for forming a conductive film of the present invention has a low specific resistance, can perform DC sputtering, and can form a transparent conductive film having high film specific resistance and high chemical resistance by sputtering. The manufacturing method of the transparent conductive film of the present invention is capable of manufacturing a transparent conductive film having high specific resistance and high chemical resistance.

The sputtering target for a transparent conductive film of the present invention includes an oxide sintered body, and the constituent elements of the oxide sintered body are In, Sn, Si, and O, and the content ratio of In is more than 25.0 in terms of In ₂ O _3. % And 82.0% by mass or less, the content ratio of Sn is 15.0% by mass or more and 65.0% by mass or less in terms of SnO ₂ , and the content ratio of Si is 3.0% by mass or more and less than 10.0% by mass in terms of SiO ₂ . A target containing an oxide sintered body, such as a sputtering target for a transparent conductive film of the present invention, naturally contains unavoidable impurities derived from raw materials and the like, and is also included in a sputtering target for a transparent conductive film of the present invention. It also contains unavoidable impurities. The content of the unavoidable impurities in the sputtering target for transparent conductive films of the present invention is usually 100 ppm or less.

In the present invention, the constituent elements refer to constituent elements other than unavoidable impurities in the sputtering target or the transparent conductive film, and the content ratio of each constituent element refers to the entire sputtering target or the transparent conductive film. The content ratio of each constituent element in.

The sputtering target for the transparent conductive film of the present invention is characterized in that the content ratio of Sn is higher than that of a normal ITO sputtering target, and the content of Si is 3.0% by mass or more and less than 10.0% in terms of SiO ₂ conversion. %.

The oxide sintering system contains In, Sn, Si, and O as constituent elements. In the oxide sintered body, the In content is more than 25.0% by mass and 82.0% by mass in terms of In ₂ O ₃ , preferably 31.0% by mass or more and 76.0% by mass or less, and more preferably 31.0% by mass or more and 70.0% by mass % Or less, the content ratio of Sn is 15.0% by mass or more and 65.0% by mass or less in terms of SnO ₂ , preferably 20.0% by mass or more and 60.0% by mass or less, more preferably 25.0% by mass or more and 60.0% by mass or less, and the content ratio of Si Based on SiO ₂ conversion, it is 3.0 mass% or more and less than 10.0 mass%, preferably 3.0 mass% or more and 9.9 mass% or less, more preferably 4.0 mass% or more and 9.0 mass% or less, and even more preferably 5.0 mass% or more and 9.0. Mass% or less. The composition of the sputtering target for a transparent conductive film is the same as that of the oxide sintered body.

A sputtering target for a transparent conductive film including an oxide sintered body having the aforementioned composition has a lower specific resistance, and therefore, DC sputtering can be performed. The specific resistance of the sputtering target for the transparent conductive film is preferably 2.0 × 10 ² Ω cm or less, more preferably 1.5 × 10 ² Ω cm or less, and even more preferably 1.0 × 10 ² Ω cm or less. Generally, DC sputtering can be performed when the specific resistance of the target is less than about 10 ² Ω cm.

A sputtering target for a transparent conductive film including an oxide sintered body having the aforementioned composition can form a transparent conductive film having a high specific resistance by sputtering. Therefore, when the transparent conductive film obtained from the aforementioned sputtering target for a transparent conductive film is used in an embedded type capacitive touch panel, it is possible to prevent the display operation from being hindered by low-frequency noise. When the sputtering target for a transparent conductive film is used, a transparent conductive film having a film specific resistance of 1.0 × 10 ⁰ Ω cm or more can be obtained. The film specific resistance of the transparent conductive film is preferably 1.1 × 10 ⁰ Ω cm or more, and more preferably 1.2 × 10 ⁰ Ω cm or more. The upper limit of the specific resistance of the transparent conductive film is not particularly limited, but is usually 5.0 × 10 ⁵ Ω cm.

A sputtering target for a transparent conductive film including an oxide sintered body having the aforementioned composition can form a transparent conductive film with high chemical resistance by sputtering. The transparent conductive film obtained from the aforementioned sputtering target for a transparent conductive film is amorphous. When the transparent conductive film is amorphous, chemical resistance is generally low. When an amorphous transparent conductive film is heat-treated and crystallized, a transparent conductive film having high chemical resistance can be obtained, but the specific resistance of the film becomes low. The transparent conductive film obtained from the sputtering target for a transparent conductive film has the characteristics of being amorphous and having high chemical resistance. High chemical resistance can be evaluated by whether the etching rate is slow. The etching rate of the transparent conductive film obtained from the aforementioned sputtering target for a transparent conductive film is preferably less than 11.0 Å / sec, more preferably 9.0 Å / sec or less, still more preferably 6.0 Å / sec or less, and even more preferably Below 5.0Å / sec. The etching rate of the transparent conductive film can be etched by immersing a part of the transparent conductive film in a transparent conductive film etching solution (ITO-07N manufactured by Kanto Chemical Co., Ltd.) which has been heated to 40 ° C for 6 minutes, and according to The difference in film thickness (level difference) and etching time between the place where the etching has been performed and the place where the etching has not been performed are calculated.

The specific resistance of a transparent conductive film obtained by sputtering a transparent conductive film composed of an oxide sintered body containing In, Sn, and Si with a sputtering target will increase as the target has more Sn and more Si. The higher the content, the higher it becomes. Therefore, in order to obtain a transparent conductive film having a high specific resistance, it is only necessary to increase at least one of the Sn content and the Si content. That is, even if the Sn content is small, as long as the Si content of the corresponding component is increased, a transparent conductive film having a high specific resistance can be obtained. However, the chemical resistance of the transparent conductive film cannot be increased if the Sn content is small even if the Si content is increased. Therefore, in order to obtain sufficient chemical resistance of the transparent conductive film, the Sn content of the target must be 15.0% by mass or more in terms of SnO ₂ conversion. When the Sn content of the target is 15.0% by mass or more in terms of SnO ₂ conversion, in order to obtain a transparent conductive film having a very high specific resistance, the Si content is only required to be 3.0% by mass or more in terms of SiO ₂ conversion. 10.0% by mass. On the other hand, when the Sn content of the target is more than 65.0% by mass in terms of SnO ₂ , the specific resistance becomes high, so DC sputtering cannot be performed. That is, the sputtering target for a transparent conductive film of the present invention can be combined with "Sn content converted to 15.0 mass% or more and 65.0 mass% or less by SnO ₂ " and "3.0 mass% or more converted to SiO ₂ and less 10.0% by mass of Si content ", and DC sputtering is performed, and the combination thereof can have both high specific resistance and high chemical resistance of the transparent conductive film after film formation.

The relative density of the aforementioned sputtering target for a transparent conductive film is preferably 98.0% or more, more preferably 98.5% or more, and still more preferably 99.0% or more. When the relative density is 98.0% or more, no bumps or arcs are generated, and efficient sputtering can be performed. The upper limit of the relative density is not particularly limited and may exceed 100%. The aforementioned relative density is a value measured according to the Archimedes method.

The said sputtering target for transparent conductive films can be manufactured by the method shown below, for example.

First, the raw material powder is mixed. The raw material powder is usually In ₂ O ₃ powder, SnO ₂ powder, and SiO ₂ powder. The In ₂ O ₃ powder, SnO ₂ powder, and SiO ₂ powder are mixed so that the contents of In, Sn, and Si in the obtained sintered body fall within the above ranges, respectively. In addition, it was confirmed that the content ratios of In ₂ O ₃ powder, SnO ₂ powder, and SiO ₂ powder in the mixed powder obtained by mixing the raw material powders are respectively the In content converted to In ₂ O ₃ in the oxide sintered body. ratio, SnO ₂ ratio in terms of containing Sn, Si and SiO ₂ in terms of the content ratio of the same.

Since the particles of each raw material powder generally exhibit agglomeration, it is preferable to pulverize and mix beforehand, or to pulverize while mixing.

The method for pulverizing and mixing the raw material powder is not particularly limited. For example, the raw material powder can be placed in a mortar and pulverized or mixed by a ball mill.

The obtained mixed powder can also be directly shaped into a shaped body and sintered, but a binder can be added to the mixed powder to form a shaped body as required. The binder may be a binder used in a known powder metallurgy method to obtain a shaped body, such as polyvinyl alcohol, an acrylic emulsion binder, or the like. In addition, a dispersant may be added to the mixed powder to prepare a slurry, the slurry may be spray-dried and dried to prepare granules, and the granules may be formed.

The forming method may be a method used in the conventional powder metallurgy, such as cold pressing, CIP (cold equalizing forming), and the like.

Further, the mixed powder may be temporarily pre-pressed to prepare a preform, and the pulverized powder obtained by the pulverization may be pressurized to form a formed body.

In addition, a molded body may be produced by a wet molding method such as a slit casting method.

The relative density of the formed body is usually 50 to 75%.

A sintered body can be obtained by firing the obtained molded body. The firing furnace used for firing is not particularly limited as long as it can control the cooling rate during cooling, and it can also be a firing furnace generally used in powder metallurgy. The firing environment is preferably an oxygen-containing environment.

From the viewpoint of high density and crack prevention, the temperature rising rate is usually 100 to 500 ° C / h. The firing temperature is 1300 to 1600 ° C, more preferably 1400 to 1600 ° C. When the firing temperature is within the aforementioned range, a high-density sintered body can be obtained. The holding time at the aforementioned firing temperature is usually 3 to 30 hours, preferably 5 to 20 hours. When the holding time is within the aforementioned range, a high-density sintered body is easily obtained.

After the temperature is maintained, the temperature in the firing furnace is lowered to be generally 300 ° C./hr or less, and preferably 100 ° C./hr or less, and cooled.

The sintered body obtained in this manner is cut into a desired shape as needed, and is polished, etc., thereby obtaining the aforementioned sputtering target for a transparent conductive film.

The shape of the sputtering target for the transparent conductive film is a flat plate shape, a cylindrical shape, or the like, and is not particularly limited.

The sputtering target for a transparent conductive film is usually used for bonding to a substrate. The substrate is usually made of Cu, Al, Ti, or stainless steel. The bonding material can be a bonding material used for bonding conventional ITO targets, for example, In metal. The bonding method is also the same as that of the conventional ITO target.

By sputtering the transparent conductive film with a sputtering target, a transparent conductive film can be formed. As described above, since the sputtering target for the transparent conductive film has a lower specific resistance, not only RF sputtering but also DC sputtering can be performed.

By sputtering the transparent conductive film with a sputtering target, a transparent conductive film having In, Sn, Si, and O as constituent elements can be obtained. The Sn content ratio and the Si content ratio of the obtained transparent conductive film tend to be lower than the Sn content ratio and the Si content ratio of the aforementioned sputtering target for a transparent conductive film. Therefore, in the aforementioned transparent conductive film, the content ratio of In is 28.0% by mass or more and 87.0% by mass in terms of In ₂ O ₃ , preferably 33.0% by mass or more and 80.0% by mass or less, and the content ratio of Sn is 12.0 in terms of SnO _2. more than 63.0% by mass% by mass or less, more preferably 18.0 mass% based 58.0 mass% or less, Si in the SiO ₂ content ratio of less than 1.0% by mass in terms of 9.0% by mass or less, preferably 2.0 mass% or more based 9.0 mass% or less. As described above, the obtained transparent conductive film has a high specific resistance and chemical resistance. Also, as in the case of the sputtering target for a transparent conductive film, the transparent conductive film may contain unavoidable impurities. The content of the unavoidable impurities in the transparent conductive film is usually 100 ppm or less.

[Example]

The measurement methods used in the following examples and comparative examples are shown below.

Target relative density

The relative density of the sputtering target for a transparent conductive film was measured according to the Archimedes method. Specifically, the air mass of the target is divided by the volume (the mass of the target in water / the specific gravity of water at the measurement temperature) to give a percentage relative to the theoretical density ρ (g / cm ³ ) according to the following formula (X) The value is taken as the relative density (unit:%).

ρ = ((C1 / 100) / ρ 1+ (C2 / 100) / ρ 2 + ‧‧‧ + (Ci / 100) / ρ i) ^-1 (X) (where C1 to Ci are the targets respectively The content (mass%) of the constituent substances, ρ 1 to ρ i represent the density (g / cm ³ ) of each constituent substance corresponding to C1 to Ci.)

Since the substances (raw materials) used for target production in the following examples and comparative examples are In ₂ O ₃ , SnO ₂ , and SiO ₂ , the theoretical density can be calculated by applying the following to formula (X), for example. ρ.

C1: mass% of In ₂ O ₃ raw material used for target

ρ 1: Density of In ₂ O ₃ (7.18g / cm ³ )

C2: mass% of SnO ₂ raw material used in the target

ρ 2: Density of SnO ₂ (6.95g / cm ³ )

C3: mass% of SiO ₂ raw material used in the target

ρ 3: Density of SiO ₂ (2.20g / cm ³ )

2. Target specific resistance

The specific resistance of the sputtering target was measured by using the Loresta (registered trademark) HP MCP-T410 (series 4 probe TYPE ESP) manufactured by Mitsubishi Chemical Corporation against the surface of the sintered body after processing, and the measurement was performed in the AUTO RANGE mode.

3. Film specific resistance of transparent conductive film

The specific resistance of the transparent conductive film was measured using a four-probe measuring instrument K-705RS manufactured by Kyowa Riken.

4. Etching rate of transparent conductive film

The etching rate of the transparent conductive film was etched by immersing a part of the transparent conductive film in a transparent conductive film etching solution (ITO-07N manufactured by Kanto Chemical Co., Ltd.) which had been heated to 40 ° C for 6 minutes, and KLA- The stylus-type surface shape measuring instrument P-15 manufactured by Tencor Corporation measures the difference in height between the place where the etching has been performed and the place where the etching has not been performed, and calculates the difference by dividing the difference between the etching time.

5.In, Sn, Si content ratio of transparent conductive film

For the measurement, a transparent conductive film formed on a copper foil was used. The content ratios of In and Sn are measured by the acid decomposition ICP-OES method using 720 ICP-OES, an ICP emission spectrophotometer made by Agilent Technologies, and the Si content ratio is measured using a spectrophotometer U-2900 manufactured by Hitachi, Ltd. Molybdenum blue absorptiometry was used for the measurement.

    [Examples and Comparative Examples]    

(Manufacture of sputtering target)

In ₂ O ₃ powder, SnO ₂ powder, and SiO ₂ powder were mixed at a ratio shown in Table 1 using a pellet mill to prepare a mixed powder.

To the aforementioned mixed powder, 6% by mass of polyvinyl alcohol diluted to 4% by mass relative to the mixed powder was added, and the powder was fully impregnated with the polyvinyl alcohol using a mortar, and passed through a 5.5-mesh sieve. The obtained powder was pre-pressed under the conditions of 200 kg / cm ² , and the obtained pre-formed body was pulverized in a mortar. The obtained pulverized material was filled in a mold for pressurization, and formed at a pressurization pressure of 1 t / cm ² for 60 seconds to obtain a molded body.

The obtained compact was placed in a firing furnace, and oxygen was flowed in the furnace at 1 L / h, and the firing environment was set to an oxygen flowing environment. The heating rate was 350 ° C / h, and the firing temperature was 1550 ° C. The firing was performed so that the holding time of the firing temperature was 9 hours.

Thereafter, it was cooled at a temperature reduction rate of 100 ° C / h.

An oxide sintered body was obtained in the above manner.

This oxide sintered body was cut to produce a sputtering target. The relative density and specific resistance of the sputtering target were measured by the methods described above. The results are shown in Table 1.

(Manufacture of transparent conductive film)

The sputtering target was bonded to a copper support plate with In solder, and sputtering was performed under the following conditions. A transparent conductive film having a thickness of 1000 Å was formed on a glass substrate for measurement of specific resistance and etching rate. A 15,000 Å transparent conductive film was formed on a copper foil having a thickness of 1.1 mm. The transparent conductive film was used to measure the Sn content ratio and Si content ratio. In Comparative Example 5, DC sputtering was not performed because the target had a high specific resistance and no discharge occurred.

Device: DC magnetron spattering device, exhaust refrigeration pump, rotary pump

Reaching vacuum degree: 1 × 10 ^-4 Pa

Sputtering pressure: 0.4Pa

Oxygen flow: 0 to 2.5 sccm

The specific resistance, the etching rate, the In content ratio, the Sn content ratio, and the Si content ratio of the obtained transparent conductive film were measured by the methods described above. The condition of the oxygen flow rate is appropriately adjusted to a condition where an amorphous transparent conductive film can be obtained and the specific resistance of the film is the lowest. The results are shown in Table 1.

Claims (9)

A sputtering target for a transparent conductive film includes an oxide sintered body, the constituent elements of the oxide sintered body are In, Sn, Si, and O, and the content ratio of In is more than 25.0% by mass in terms of In ₂ O ₃ and 82.0% by mass or less, the content ratio of Sn in terms of SnO ₂ is 15.0% by mass or more and 65.0% by mass or less, and the content ratio of Si in terms of SiO ₂ is 3.0% by mass or more and less than 10.0% by mass. The sputter target for a transparent conductive film as described in item 1 of the scope of the patent application has a specific resistance of 2.0 × 10 ² Ω cm or less.     The relative density of the sputtering target for a transparent conductive film as described in item 1 or 2 of the patent application range is 98.0% or more.     A transparent conductive film whose constituent elements are In, Sn, Si, and O, and the content ratio of In is 28.0% by mass or more and 87.0% by mass in terms of In ₂ O ₃ , and the content ratio of Sn is 12.0% by mass in terms of SnO ₂ . Above 63.0% by mass, the content ratio of Si is 1.0% by mass or more and 9.0% by mass or less in terms of SiO ₂ conversion. The transparent conductive film described in item 4 of the scope of application for a patent has a film specific resistance of 1.0 × 10 ⁰ Ω cm or more.     For the transparent conductive film described in item 4 or 5 of the patent application scope, the etching rate is less than 11.0 Å / sec.         A method for manufacturing a transparent conductive film is formed by sputtering a sputtering target for a transparent conductive film as described in any one of items 1 to 3 of the patent application scope.     The method for manufacturing a transparent conductive film according to item 7 of the scope of the patent application, wherein the film specific resistance of the transparent conductive film is 1.0 × 10 ⁰ Ω cm or more.     According to the manufacturing method of the transparent conductive film according to item 7 or 8 of the scope of the applied patent, wherein the etching rate of the transparent conductive film is less than 11.0 Å / sec.